Expression of serine/glycine metabolism-related proteins is different according to the thyroid cancer subtype

Reprogramming of Thyroid Cancer Metabolism: from Mechanism to Therapeutic Strategy

Thyroid cancer as one of the most prevalent malignancies of endocrine system, has raised public concern and more research on its mechanism and treatment. And metabolism-based therapies have advanced rapidly, for the exclusive metabolic profiling of thyroid cancer. In thyroid cancer cells, plenty of metabolic pathways are reprogrammed to accommodate tumor microenvironment. In this review, we initiatively summarize recent progress in the full-scale thyroid cancer metabolic rewiring and the interconnection of various metabolites. We also discuss the efficacy and prospect of metabolic targeted detection as well as therapy. Comprehending metabolic mechanism and characteristics of thyroid cancer roundly will be highly beneficial to managing individual patients.

PHGDH Induction by MAPK Is Essential for Melanoma Formation and Creates an Actionable Metabolic Vulnerability

Overexpression of phosphoglycerate dehydrogenase (PHGDH), the rate-limiting enzyme in the serine synthesis pathway, promotes melanomagenesis, melanoma cell proliferation, and survival of metastases in serine-low environments such as the brain. Here, we found that PHGDH is universally increased in melanoma cells and required for melanomagenesis. Although PHGDH amplification explained PHGDH overexpression in a subset of melanomas, oncogenic BRAFV600E also promoted PHGDH transcription through mTORC1-mediated translation of ATF4. Importantly, depletion of PHGDH in genetic mouse melanoma models blocked tumor formation. In addition to BRAFV600E-mediated upregulation, PHGDH was further induced by exogenous serine restriction. Surprisingly, BRAFV600E inhibition diminished serine restriction-mediated PHGDH expression by preventing ATF4 induction. Consequently, melanoma cells could be specifically starved of serine by combining BRAFV600E inhibition with exogenous serine restriction, which promoted cell death in vitro and attenuated melanoma growth in vivo. In summary, this study identified that PHGDH is essential for melanomagenesis and regulated by BRAFV600E, revealing a targetable vulnerability in BRAFV600E-mutant melanoma. Significance: BRAFV600E promotes the expression of the serine synthesis enzyme PHGDH, which is required for melanoma formation, and can be targeted to sensitize melanoma to dietary serine restriction, providing a melanoma cell-specific treatment strategy.

Emerging role of metabolic reprogramming in the immune microenvironment and immunotherapy of thyroid cancer

The metabolic reprogramming of cancer cells is a hallmark of many malignancies. To meet the energy acquisition needs of tumor cells for rapid proliferation, tumor cells reprogram their nutrient metabolism, which is caused by the abnormal expression of transcription factors and signaling molecules related to energy metabolic pathways as well as the upregulation and downregulation of abnormal metabolic enzymes, receptors, and mediators. Thyroid cancer (TC) is the most common endocrine tumor, and immunotherapy has become the mainstream choice for clinical benefit after the failure of surgical, endocrine, and radioiodine therapies. TC change the tumor microenvironment (TME) through nutrient competition and metabolites, causing metabolic reprogramming of immune cells, profoundly changing immune cell function, and promoting immune evasion of tumor cells. A deeper understanding of how metabolic reprogramming alters the TME and controls immune cell fate and function will help improve the effectiveness of TC immunotherapy and patient outcomes. This paper aims to elucidate the metabolic communication that occurs between immune cells around TC and discusses how metabolic reprogramming in TC affects the immune microenvironment and the effectiveness of anti-cancer immunotherapy. Finally, targeting key metabolic checkpoints during metabolic reprogramming, combined with immunotherapy, is a promising strategy.

Bioinformatics analysis of PSAT1 loss identifies downstream pathways regulated in EGFR mutant NSCLC and a selective gene signature for predicting the risk of relapse

The majority of malignant tumors exhibit an altered metabolic phenotype that ultimately provides the required energy and molecular precursors necessary for unregulated cell division. Within this, phosphoserine aminotransferase 1 (PSAT1) is involved in de novo serine biosynthesis and its activity promotes various biochemical processes, including one-carbon metabolism. It also directly generates α-ketoglutarate (α-KG), a Kreb cycle intermediate and epigenetic-regulating metabolite. Prior studies examining PSAT1 depletion have identified individual affected downstream pathways, such as GSK3β and E2F, in several cancer types, including non-small-cell lung cancer (NSCLC). However, global gene expression examination in response to PSAT1 loss, particularly in EGFR mutant NSCLC, has not been unexplored. Transcriptional profiling of EGFR mutant NSCLC cells with or without stable knock-down of PSAT1 identified differentially expressed genes (DEGs) enriched in several metabolic pathways required for cell division, including amino acid and nucleotide biosynthesis. Supplementation studies involving non-essential amino acids, nucleosides and α-KG partially restored defects in anchorage-independent growth due to the knockdown of PSAT1. Kyoto Encyclopedia of Genes and Genomes and Gene Ontology enrichment analysis identified potential impacts on actin cytoskeleton arrangement and β-catenin activity, which were rescued by PSAT1 re-expression. Finally, a comparative analysis of PSAT1 DEGs against transcripts enriched in patient EGFR mutant lung tumors identified a gene signature that is associated with overall and relapse-free survival (RFS) and was able to distinguish low or high-risk populations for RFS in early-stage EGFR mutant NSCLC. Overall, investigating genes altered by PSAT1 loss confirmed known PSAT1-regulated cellular pathways, identified a previously unknown role in the mediation of cytoskeleton arrangement in EGFR mutant NSCLC cells and allowed for the characterization of a gene signature with putative predictive potential for RFS in early-stage disease.

Dual Immune Checkpoint Inhibition in Patients With Aggressive Thyroid Carcinoma: A Phase 2 Nonrandomized Clinical Trial

Importance

Aggressive thyroid carcinoma, including radioiodine refractory (RAIR) differentiated thyroid carcinoma (DTC), medullary thyroid carcinoma (MTC), and anaplastic thyroid carcinoma (ATC), are associated with significant morbidity and mortality and have limited therapeutic options. Distinct immune profiles have been identified in thyroid cancer subtypes suggesting they may be susceptible to immune checkpoint inhibition.

Objective

To evaluate the efficacy of anti-programmed cell death 1 nivolumab and anti-cytotoxic lymphocyte-associated protein 4 ipilimumab in patients with aggressive thyroid carcinoma.

Design, Setting, and Participants

This phase 2 nonrandomized clinical trial enrolled patients with RAIR DTC in a single center from October 2017 to May 2019, with exploratory cohorts in MTC and ATC. The data were analyzed between June 2021 and September 2023.

Intervention

Intravenous nivolumab, 3 mg/kg, every 2 weeks and ipilimumab, 1 mg/kg, every 6 weeks until disease progression, intolerable adverse events, or a maximum duration of 2 years.

Main Outcomes and Measures

The primary end point of the study was objective response rate (ORR) in RAIR DTC, which was scored according to RECIST (Response Evaluation Criteria in Solid Tumours), version 1.1. Key secondary end points included safety, progression-free survival, overall survival, and biomarker analyses.

Results

A total of 51 patients were registered, and 49 patients were evaluable for analysis. The median (range) age was 65 years (30-88 years), and 25 participants (51%) were female. ORR in the DTC cohort was 9.4% (3/32 [95% CI, 2.8%-28.5%]), with all partial responses in either oncocytic carcinoma (2/6 [33.0%]) or poorly differentiated thyroid carcinoma (1/5 [20.0%]). Clinical benefit rates were 62.5% (20/32) in the overall DTC cohort, including 83.3% (5/6) in oncocytic carcinoma and 40% (2/5) in poorly differentiated thyroid carcinoma. ORR in the exploratory ATC cohort was 30.0% (3/10 [95% CI, 6.7%-65.2%]), with a clinical benefit rates of 50.0% (5/10). No responses were observed in the exploratory MTC cohort. The safety profile was similar to prior reports with dual immune checkpoint inhibition (pruritus, rash, diarrhea, fatigue, and elevation of lipase and liver enzymes). The presence of NRAS tumor genetic sequence variations, but not BRAF V600E, was associated with worse outcomes.

Conclusions and Relevance

This phase 2 nonrandomized clinical trial reported clinical activity of dual immune checkpoint inhibition in aggressive thyroid cancer. The study did not meet its end point in the primary population of RAIR DTC and does not support further investigation in non-biomarker-selected DTC. However, the signal observed in ATC may merit further evaluation.

Trial Registration

ClinicalTrials.gov Identifier: NCT03246958.

PDPR Gene Variants Predisposing to Papillary Thyroid Cancer

Background: Papillary thyroid cancer (PTC) is the predominant subtype of thyroid cancer (THCA), and it can cluster in families with an autosomal dominant (AD) inheritance pattern. The aim of this study was to identify novel genes and mechanisms underlying PTC susceptibility. Methods: Our previous investigation of 17 AD PTC families led us to conduct a deeper analysis on one family (Family Q) with whole-genome sequencing data from 3 PTC-affected individuals. In addition, 323 sporadic THCA cases from Avatar data and 12 familial adenomatous polyposis (FAP) individuals with secondary THCA were screened for pyruvate dehydrogenase phosphatase regulatory (PDPR) variants. CRISPR-Cas9 was used to create PDPR-deficient THCA (TPC1) and transformed normal thyroid cell lines (N-Thyori3-1) to study the metabolic consequences of PDPR loss. Results: We found truncating PDPR splice donor variants (NM_017990.4:c.361 + 1G>C) in all affected PTC Family Q members, and another PDPR splice donor variant (NM_017990.4:c.443 + 1G>C) in a sporadic PTC case. In addition, an ultra-rare missense variant was found in an FAP-PTC patient. The PDPR-deficient cells presented with elevated phosphorylation of pyruvate dehydrogenase and altered glucose metabolism, implying that PDPR plays an essential part in regulating glucose metabolism in thyroid cells. Conclusions: Our finding of novel truncating germline variants in PDPR in Family Q and additional cohorts suggests a role for PDPR loss in PTC predisposition. Also, somatic and RNA sequencing from the thyroid carcinoma (Firehouse Legacy) data showed that PDPR gene expression is much lower in THCA tumor tissue compared with matching normal tissue. Thus, PDPR appears to have a loss of function effect on THCA tumorigenesis.

MAPK-mediated PHGDH induction is essential for melanoma formation and represents an actionable vulnerability

Overexpression of PHGDH, the rate-limiting enzyme in the serine synthesis pathway, promotes melanomagenesis, melanoma cell proliferation, and survival of metastases in serine-low environments such as the brain. While PHGDH amplification explains PHGDH overexpression in a subset of melanomas, we find that PHGDH levels are universally increased in melanoma cells due to oncogenic BRAFV600E promoting PHGDH transcription through mTORC1-mediated translation of ATF4. Importantly, PHGDH expression was critical for melanomagenesis as depletion of PHGDH in genetic mouse models blocked melanoma formation. Despite BRAFV600E-mediated upregulation, PHGDH was further induced by exogenous serine restriction. Surprisingly, BRAFV600E inhibition diminished serine restriction-mediated PHGDH expression by preventing ATF4 induction, creating a potential vulnerability whereby melanoma cells could be specifically starved of serine by combining BRAFV600E inhibition with exogenous serine restriction. Indeed, we show that this combination promoted cell death in vitro and attenuated melanoma growth in vivo. This study identified a melanoma cell-specific PHGDH-dependent vulnerability.

Targeting serine/glycine metabolism improves radiotherapy response in non-small cell lung cancer

BACKGROUND

Lung cancer is the most lethal cancer, and 85% of cases are classified as non-small cell lung cancer (NSCLC). Metabolic rewiring is a cancer hallmark that causes treatment resistance, and lacks insights into serine/glycine pathway adaptations upon radiotherapy.

METHODS

We analyzed radiotherapy responses using mass-spectrometry-based metabolomics in NSCLC patient's plasma and cell lines. Efficacy of serine/glycine conversion inhibitor sertraline with radiotherapy was investigated by proliferation, clonogenic and spheroid assays, and in vivo using a serine/glycine dependent NSCLC mouse model by assessment of tumor growth, metabolite and cytokine levels, and immune signatures.

RESULTS

Serine/glycine pathway metabolites were significantly consumed in response to radiotherapy in NSCLC patients and cell models. Combining sertraline with radiotherapy impaired NSCLC proliferation, clonogenicity and stem cell self-renewal capacity. In vivo, NSCLC tumor growth was reduced solely in the sertraline plus radiotherapy combination treatment group. Tumor weights linked to systemic serine/glycine pathway metabolite levels, and were inhibited in the combination therapy group. Interestingly, combination therapy reshaped the tumor microenvironment via cytokines associated with natural killer cells, supported by eradication of immune checkpoint galectin-1 and elevated granzyme B levels.

CONCLUSION

Our findings highlight that targeting serine/glycine metabolism using sertraline restricts cancer cell recovery from radiotherapy and provides tumor control through immunomodulation in NSCLC.

Integrative Multi-omics Analysis Reveals Different Metabolic Phenotypes Based on Molecular Characteristics in Thyroid Cancer

PURPOSE

Thyroid cancer metabolic characteristics vary depending on the molecular subtype determined by mutational status. We aimed to investigate the molecular subtype-specific metabolic characteristics of thyroid cancers.

EXPERIMENTAL DESIGN

An integrative multi-omics analysis was conducted, incorporating transcriptomics, metabolomics, and proteomics data obtained from human tissues representing distinct molecular characteristics of thyroid cancers: BRAF-like (papillary thyroid cancer with BRAFV600E mutation; PTC-B), RAS-like (follicular thyroid cancer with RAS mutation; FTC-R), and ATC-like (anaplastic thyroid cancer with BRAFV600E or RAS mutation; ATC-B or ATC-R). To validate our findings, we employed tissue microarray of human thyroid cancer tissues and performed in vitro analyses of cancer cell phenotypes and metabolomic assays after inducing genetic knockdown.

RESULTS

Metabolic properties differed between differentiated thyroid cancers of PTC-B and FTC-R, but were similar in dedifferentiated thyroid cancers of ATC-B/R, regardless of their mutational status. Tricarboxylic acid (TCA) intermediates and branched-chain amino acids (BCAA) were enriched with the activation of TCA cycle only in FTC-R, whereas one-carbon metabolism and pyrimidine metabolism increased in both PTC-B and FTC-R and to a great extent in ATC-B/R. However, the protein expression levels of the BCAA transporter (SLC7A5) and a key enzyme in one-carbon metabolism (SHMT2) increased in all thyroid cancers and were particularly high in ATC-B/R. Knockdown of SLC7A5 or SHMT2 inhibited the migration and proliferation of thyroid cancer cell lines differently, depending on the mutational status.

CONCLUSIONS

These findings define the metabolic properties of each molecular subtype of thyroid cancers and identify metabolic vulnerabilities, providing a rationale for therapies targeting its altered metabolic pathways in advanced thyroid cancer.

Unraveling the role of the mitochondrial one-carbon pathway in undifferentiated thyroid cancer by multi-omics analyses

The role of the serine/glycine metabolic pathway (SGP) has recently been demonstrated in tumors; however, the pathological relevance of the SGP in thyroid cancer remains unexplored. Here, we perform metabolomic profiling of 17 tumor-normal pairs; bulk transcriptomics of 263 normal thyroid, 348 papillary, and 21 undifferentiated thyroid cancer samples; and single-cell transcriptomes from 15 cases, showing the impact of mitochondrial one-carbon metabolism in thyroid tumors. High expression of serine hydroxymethyltransferase-2 (SHMT2) and methylenetetrahydrofolate dehydrogenase 2 (MTHFD2) is associated with low thyroid differentiation scores and poor clinical features. A subpopulation of tumor cells with high mitochondrial one-carbon pathway activity is observed in the single-cell dataset. SHMT2 inhibition significantly compromises mitochondrial respiration and decreases cell proliferation and tumor size in vitro and in vivo. Collectively, our results highlight the importance of the mitochondrial one-carbon pathway in undifferentiated thyroid cancer and suggest that SHMT2 is a potent therapeutic target.

Diagnostics of Thyroid Cancer Using Machine Learning and Metabolomics

The objective of this research is, with the analysis of existing data of thyroid cancer (TC) metabolites, to develop a machine-learning model that can diagnose TC using metabolite biomarkers. Through data mining, pathway analysis, and machine learning (ML), the model was developed. We identified seven metabolic pathways related to TC: Pyrimidine metabolism, Tyrosine metabolism, Glycine, serine, and threonine metabolism, Pantothenate and CoA biosynthesis, Arginine biosynthesis, Phenylalanine metabolism, and Phenylalanine, tyrosine, and tryptophan biosynthesis. The ML classifications' accuracies were confirmed through 10-fold cross validation, and the most accurate classification was 87.30%. The metabolic pathways identified in relation to TC and the changes within such pathways can contribute to more pattern recognition for diagnostics of TC patients and assistance with TC screening. With independent testing, the model's accuracy for other unique TC metabolites was 92.31%. The results also point to a possibility for the development of using ML methods for TC diagnostics and further applications of ML in general cancer-related metabolite analysis.

Anti-leukemia effects of omipalisib in acute myeloid leukemia: inhibition of PI3K/AKT/mTOR signaling and suppression of mitochondrial biogenesis

Omipalisib (GSK2126458), a potent dual PI3K/mTOR inhibitor, is reported to exhibit anti-tumor effect in several kinds of cancers. More than 50% of acute myeloid leukemia (AML) patients display a hyperactivation of PI3K/AKT/mTOR signaling. We investigated the anti-proliferative effect of omipalisib in AML cell lines with varied genetic backgrounds. The OCI-AML3 and THP-1 cell lines had a significant response to omipalisib, with IC50 values of 17.45 nM and 8.93 nM, respectively. We integrated transcriptomic profile and metabolomic analyses, and followed by gene set enrichment analysis (GSEA) and metabolite enrichment analysis. Our findings showed that in addition to inhibiting PI3K/AKT/mTOR signaling and inducing cell cycle arrest at the G0/G1 phase, omipalisib also suppressed mitochondrial respiration and biogenesis. Furthermore, omipalisib downregulated several genes associated with serine, glycine, threonine, and glutathione metabolism, and decreased their protein and glutathione levels. In vivo experiments revealed that omipalisib significantly inhibited tumor growth and prolonged mouse survival without weight loss. Gedatolisib and dactolisib, another two PI3K/mTOR inhibitors, exerted similar effects without affecting mitochondria biogenesis. These results highlight the multifaceted anti-leukemic effect of omipalisib, revealing its potential as a novel therapeutic agent in AML treatment.

Experimental study on changes in metabolic mechanism of papillary thyroid carcinoma complicated with Hashimoto's thyroiditis

Background

Whether the mechanism of thyroid papillary carcinoma (PTC) is the same in patients with a Hashimoto's thyroiditis (HT) background as compared with patients with a normal background remains a highly debated and controversial issue. In this study, we aimed to analyze the differences and similarities of the metabolic mechanism of PTC in normal and HT background, and to explore the relationship between HT and PTC.

Methods

The ultra performance liquid chromatography-quadrupole-time of flight-mass spectrometry (UPLC-Q-TOF/MS) technology was used to analyze 61 PTC patient tissues (31 HT background and 30 normal tissue (NC) background). Potential biomarkers were screened from principal component analysis (PCA) to orthogonal partial least square (OPLS) discriminant analysis. HMDB was searched to identify potential differential metabolites and final metabolic pathway analysis was performed by MetaboAnalyst 5.0. We analyzed the differential metabolites diagnostic accuracy through receiver operating characteristic (ROC) curves analysis.

Results

Seven different metabolites were screened from HT group and NC group, including arginine, glutamic acid, cysteine, citric acid, malic acid, uracil and taurine. Logistic regression model combined with ROC analysis of these 7 biomarkers had good discriminability for PTC (area under operating characteristic curve of HT group and NC group were 0.867 and 0.973, respectively). The HT group had specific metabolic pathways, including aminoacyl-tRNA biosynthesis, glycine, serine and threonine metabolism.

Conclusions

The metabolic profiles of the NC and HT groups had important similarities and differences in PTC. The correlation of PTC with HT may be related to aminoacyl-tRNA biosynthesis, serine and threonine metabolism.

Glycine Decarboxylase (GLDC) Plays a Crucial Role in Regulating Energy Metabolism, Invasion, Metastasis and Immune Escape for Prostate Cancer

Glycine decarboxylase (GLDC) is one of the core enzymes for glycine metabolism, and its biological roles in prostate cancer (PCa) are unclear. First, we found that GLDC plays a central role in glycolysis in 540 TCGA PCa patients. Subsequently, a metabolomic microarray showed that GLDC enhanced aerobic glycolysis in PCa cells, and GLDC and its enzyme activity enhanced glucose uptake, lactate production and lactate dehydrogenase (LDH) activity in PCa cells. Next, we found that GLDC was highly expressed in PCa, was directly regulated by hypoxia-inducible factor (HIF1-α) and regulated downstream LDHA expression. In addition, GLDC and its enzyme activity showed a strong ability to promote the migration and invasion of PCa both in vivo and in vitro. Furthermore, we found that the GLDC-high group had a higher TP53 mutation frequency, lower CD8+ T-cell infiltration, higher immune checkpoint expression, and higher immune exclusion scores than the GLDC-low group. Finally, the GLDC-based prognostic risk model by applying LASSO Cox regression also showed good predictive power for the clinical characteristics and survival in PCa patients. This evidence indicates that GLDC plays crucial roles in glycolytic metabolism, invasion and metastasis, and immune escape in PCa, and it is a potential therapeutic target for prostate cancer.

Serine-associated one-carbon metabolic reprogramming: a new anti-cancer therapeutic strategy

Tumour metabolism is a major focus of cancer research, and metabolic reprogramming is an important feature of malignant tumours. Serine is an important non-essential amino acid, which is a main resource of one-carbon units in tumours. Cancer cells proliferate more than normal cells and require more serine for proliferation. The cancer-related genes that are involved in serine metabolism also show changes corresponding to metabolic alterations. Here, we reviewed the serine-associated one-carbon metabolism and its potential as a target for anti-tumour therapeutic strategies.

Co-inhibition of glutaminolysis and one-carbon metabolism promotes ROS accumulation leading to enhancement of chemotherapeutic efficacy in anaplastic thyroid cancer

Anaplastic thyroid cancer (ATC) is one of the most aggressive tumors with an extremely poor prognosis. Based on the several biological features related to glutamine metabolism in ATC, we hypothesized glutaminolysis inhibition induces cell death in ATC cells. However, glutamine metabolism inhibition triggered cell growth arrest independent of cell death in ATC, suggesting that other signaling pathways avoid glutamine metabolism inhibition-induced stress exist. To investigate the functional mechanism against glutamine metabolism inhibition, we conducted mRNA and ATAC-Sequencing data analysis and found that glutamine deprivation increased ATF4-mediated one-carbon metabolism. When we inhibited PHGDH, the first rate-limiting enzyme for one-carbon metabolism, cell growth arrest was promoted upon glutamine metabolism inhibition by accumulating intracellular ROS. We next observed that the co-inhibition of glutamine and one-carbon metabolism could augment the anticancer effects of drugs used in patients with ATC. Finally, single-cell RNA sequencing analysis revealed that one-carbon metabolism was strengthened through the evolutionary process from PTC to ATC. Collectively, our data demonstrate that one-carbon metabolism has a potential role of modulation of cell fate in metabolic stress and can be a therapeutic target for enhancing antitumor effects in ATC.

Cancer metabolites: promising biomarkers for cancer liquid biopsy

Cancer exerts a multitude of effects on metabolism, including the reprogramming of cellular metabolic pathways and alterations in metabolites that facilitate inappropriate proliferation of cancer cells and adaptation to the tumor microenvironment. There is a growing body of evidence suggesting that aberrant metabolites play pivotal roles in tumorigenesis and metastasis, and have the potential to serve as biomarkers for personalized cancer therapy. Importantly, high-throughput metabolomics detection techniques and machine learning approaches offer tremendous potential for clinical oncology by enabling the identification of cancer-specific metabolites. Emerging research indicates that circulating metabolites have great promise as noninvasive biomarkers for cancer detection. Therefore, this review summarizes reported abnormal cancer-related metabolites in the last decade and highlights the application of metabolomics in liquid biopsy, including detection specimens, technologies, methods, and challenges. The review provides insights into cancer metabolites as a promising tool for clinical applications.

Characterization of metabolic reprogramming by metabolomics in the oncocytic thyroid cancer cell line XTC.UC1

Oncocytic thyroid cancer is characterized by the aberrant accumulation of abnormal mitochondria in the cytoplasm and a defect in oxidative phosphorylation. We performed metabolomics analysis to compare metabolic reprogramming among the oncocytic and non-oncocytic thyroid cancer cell lines XTC.UC1 and TPC1, respectively, and a normal thyroid cell line Nthy-ori 3-1. We found that although XTC.UC1 cells exhibit higher glucose uptake than TPC1 cells, the glycolytic intermediates are not only utilized to generate end-products of glycolysis, but also diverted to branching pathways such as lipid metabolism and the serine synthesis pathway. Glutamine is preferentially used to produce glutathione to reduce oxidative stress in XTC.UC1 cells, rather than to generate α-ketoglutarate for anaplerotic flux into the TCA cycle. Thus, growth, survival and redox homeostasis of XTC.UC1 cells rely more on both glucose and glutamine than do TPC1 cells. Furthermore, XTC.UC1 cells contained higher amounts of intracellular amino acids which is due to higher expression of the amino acid transporter ASCT2 and enhanced autophagy, thus providing the building blocks for macromolecules and energy production. These metabolic alterations are required for oncocytic cancer cells to compensate their defective mitochondrial function and to alleviate excess oxidative stress.

Reprogramming of Cellular Metabolism and Its Therapeutic Applications in Thyroid Cancer

Metabolism is a series of life-sustaining chemical reactions in organisms, providing energy required for cellular processes and building blocks for cellular constituents of proteins, lipids, carbohydrates and nucleic acids. Cancer cells frequently reprogram their metabolic behaviors to adapt their rapid proliferation and altered tumor microenvironments. Not only aerobic glycolysis (also termed the Warburg effect) but also altered mitochondrial metabolism, amino acid metabolism and lipid metabolism play important roles for cancer growth and aggressiveness. Thus, the mechanistic elucidation of these metabolic changes is invaluable for understanding the pathogenesis of cancers and developing novel metabolism-targeted therapies. In this review article, we first provide an overview of essential metabolic mechanisms, and then summarize the recent findings of metabolic reprogramming and the recent reports of metabolism-targeted therapies for thyroid cancer.

Glycine Decarboxylase Suppresses the Renal Cell Carcinoma Growth and Regulates Its Gene Expressions and Functions

Background

Glycine decarboxylase (GLDC), a key metabolic enzyme, participates in the regulation of the glycine metabolic pathway. Differential expression of GLDC is linked to the malignant growth of renal cell carcinoma (RCC) and may regulate tumor progression through other genes. However, the regulatory function of GLDC in RCC is currently unknown. The purpose of this work was to evaluate the roles of GLDC in the invasion, proliferation, and migration of RCC cells and elucidate the processes underlying RCC development.

Methods

The expression of GLDC in RCC cell lines and tissues was identified by quantitative reverse transcription polymerase chain reaction (PCR) and western blot. A stably transfected cell line overexpressing GLDC was constructed using a lentiviral vector. Cell proliferation was detected using Cell Counting Kit-8 (CCK8) and EdU experiments, and scratch and transwell assays were used to determine migration and invasion capabilities. Furthermore, differential proteins were identified and obtained using high-performance liquid chromatography (HPLC)-tandem mass spectrometry (MS/MS) analysis. Finally, these differential proteins were analyzed by bioinformatics, including cluster analysis, subcellular localization, domain annotation, annotation of the Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG), enrichment analysis, and study of protein-protein interactions.

Results

GLDC expression was found to be lower in six RCC cell lines (786-O, A498, Caki-1, 769-P, OSRC-2, and ACHN) than in 293T cells and decreased in kidney cancer tissues compared to neighboring normal tissues. Overexpression of GLDC inhibited the proliferation of RCC cells as well as their migration and invasion abilities. Tandem mass tag analysis showed that 317 and 236 genes were downregulated and upregulated, respectively, when GLDC was overexpressed in A498 cells. Tandem mass tag analysis showed that 317 and 236 genes were downregulated and upregulated, respectively, when GLDC was overexpressed in A498 cells. Volcano plot showed these upregulated and downregulated proteins. Cluster analysis showed that differentially expressed protein screening can represent the effect of biological treatment on samples. Subcellular localization analysis showed differential proteins are mainly distributed in the nucleus, cytoplasm, mitochondria, plasma membrane, extracellular matrix, and lysosome. GO annotation showed many biological processes in the cells were changed, including "positive regulation of histone H3-K4 methylation", "cofactor binding", and "nuclear body". KEGG pathway analysis showed key pathways have all undergone considerable alterations, such as "cell cycle", "glyoxylate and dicarboxylate metabolism", and "threonine, glycine, and serine metabolism". Finally, highly aggregated proteins with the same or similar functions were acquired by analysis of the protein-protein interaction (PPI) network.

Conclusions

These studies indicate that GLDC overexpression suppresses the invasion, proliferation, and migration of RCC cells and leads to the upregulation and downregulation of 236 and 317 genes, respectively.

Phosphoserine phosphatase as an indicator for survival through potentially influencing the infiltration levels of immune cells in neuroblastoma

Introduction: Metabolic deregulation, a hallmark of cancer, fuels cancer cell growth and metastasis. Phosphoserine phosphatase (PSPH), an enzyme of the serine metabolism pathway, has been shown to affect patients’ prognosis in many cancers but its significance in neuroblastoma remains unknown. Here, we show that the functional role and potential mechanism of PSPH and it is correlated with survival of neuroblastoma patients.

Patients and Methods: The TARGET dataset (n = 151) and our hospital-based cases (n = 55) were used for assessing the expression level of PSPH associated with survival in neuroblastoma patients, respectively. Then, in vitro experiments were performed to define the role of PSPH in neuroblastoma. The ESTIMATE and TIMER algorithms were utilized to examine the correlation between PSPH expression level and abundance of immune cells. Further, Kaplan-Meier survival analysis was performed to evaluate the effect of both PSPH and immune cells on patients’ prognosis.

Results: High expression of PSPH was significantly associated with unfavorable overall survival (OS) and event-free survival (EFS) in both the TARGET dataset and our hospital-based cases, and was an independent predictor of OS (hazard ratio, 2.00; 95% confidence intervals, 1.21–3.30, p = 0.0067). In vitro experiments showed that high expression of PSPH significantly promoted cell growth and metastasis. Further, the ESTIMATE result suggested that high expression level of PSPH was negatively associated with low stromal and ESTIMATE score. Specifically, high PSPH expression was found to be negatively associated with CD8⁺ T cell, macrophages and neutrophils, which negatively affected survival of neuroblastoma patients (p < 0.0001, p = 0.0005, and p = 0.0004, respectively).

Conclusion: These findings suggested that PSPH expression could be a promising indicator for prognosis and immunotherapy in neuroblastoma patients by potentially influencing infiltration levels of immune cells.

Modulation of RNA Splicing by Oligonucleotides: Mechanisms of Action and Therapeutic Implications

Dysregulation of RNA splicing causes many diseases and disorders. Several therapeutic approaches have been developed to correct aberrant alternative splicing events for the treatment of cancers and hereditary diseases, including gene therapy and redirecting splicing, using small molecules or splice switching oligonucleotides (SSO). Significant advances in the chemistry and pharmacology of nucleic acid have led to the development of clinically approved SSO drugs for the treatment of spinal muscular dystrophy and Duchenne muscular dystrophy (DMD). In this review, we discuss the mechanisms of SSO action with emphasis on "less common" approaches to modulate alternative splicing, including bipartite and bifunctional SSO, oligonucleotide decoys for splice factors and SSO-mediated mRNA degradation via AS-NMD and NGD pathways. We briefly discuss the current progress and future perspectives of SSO therapy for rare and ultrarare diseases.

Development of Metabolic Synthetic Lethality and Its Implications for Thyroid Cancer

Cancer therapies targeting genetic alterations are a topic of great interest in the field of thyroid cancer, which frequently harbors mutations in the RAS, RAF, and RET genes. Unfortunately, U.S. Food and Drug Administration-approved BRAF inhibitors have relatively low therapeutic efficacy against BRAF-mutant thyroid cancer; in addition, the cancer often acquires drug resistance, which prevents effective treatment. Recent advances in genomics and transcriptomics are leading to a more complete picture of the range of mutations, both driver and messenger, present in thyroid cancer. Furthermore, our understanding of cancer suggests that oncogenic mutations drive tumorigenesis and induce rewiring of cancer cell metabolism, which promotes survival of mutated cells. Synthetic lethality (SL) is a method of neutralizing mutated genes that were previously considered untargetable by traditional genotype-targeted treatments. Because these metabolic events are specific to cancer cells, we have the opportunity to develop new therapies that target tumor cells specifically without affecting healthy tissue. Here, we describe developments in metabolism-based cancer therapy, focusing on the concept of metabolic SL in thyroid cancer. Finally, we discuss the essential implications of metabolic reprogramming and its role in the future direction of SL for thyroid cancer.

Phosphoserine phosphatase as a prognostic biomarker in patients with gastric cancer and its potential association with immune cells

Background

Because of dismal prognosis in gastric cancer, identifying relevant prognostic factors is necessary. Phosphoserine phosphatase (PSPH) exhibits different expression patterns in many cancers and has been reported to affect the prognosis of patients with cancer. In this study, we examined the prognostic role of metabolic gene PSPH in gastric cancer based on the TCGA dataset and our hospital–based cohort cases.

Methods

We collected and analysed RNA-seq data of Pan-cancer and gastric cancer in the TCGA dataset and PSPH expression data obtained from immunohistochemical analysis of 243 patients with gastric cancer from Sun Yat-sen University cancer center. Further, Kaplan–Meier survival analysis and Cox analysis were used to assess the effect of PSPH on prognosis. The ESTIMATE and Cibersort algorithms were used to elucidate the relationship between PSPH and the abundance of immune cells using the TCGA dataset.

Results

We observed that PSPH expression displayed considerably high in gastric cancer and it was significantly associated with inferior prognosis (P = 0.043). Surprisingly, there was a significant relationship between lower immune scores and high expression of PSPH (P < 0.05). Furthermore, patients with a low amount of immune cells exhibited poor prognosis (P = 0.046). The expression of PSPH significantly increased in activated memory CD4 T cells, resting NK cells and M0 macrophages (P = 0.037, < 0.001, and 0.005, respectively).

Conclusions

This study highlighted that PSPH influences the prognosis of patients with gastric cancer, and this is associated with the infiltration of tumour immune cells, indicating that PSPH may be a new immune-related target for treating gastric cancer.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12876-021-02073-0.

Metabolic Reprogramming of Thyroid Cancer Cells and Crosstalk in Their Microenvironment

Metabolism differs significantly between tumor and normal cells. Metabolic reprogramming in cancer cells and metabolic interplay in the tumor microenvironment (TME) are important for tumor formation and progression. Tumor cells show changes in both catabolism and anabolism. Altered aerobic glycolysis, known as the Warburg effect, is a well-recognized characteristic of tumor cell energy metabolism. Compared with normal cells, tumor cells consume more glucose and glutamine. The enhanced anabolism in tumor cells includes de novo lipid synthesis as well as protein and nucleic acid synthesis. Although these forms of energy supply are uneconomical, they are required for the functioning of cancer cells, including those in thyroid cancer (TC). Increasing attention has recently focused on alterations of the TME. Understanding the metabolic changes governing the intricate relationship between TC cells and the TME may provide novel ideas for the treatment of TC.

Chemical Components of the Fruits of Morus nigra Linn.: Methyl Caffeate as a Potential Anticancer Agent by Targeting 3-Phosphoglycerate Dehydrogenase

Two previously undescribed compounds, moranigrine A (1) and morusamine (2), along with 18 known compounds were isolated from the fruits of Morus nigra Linn. and structurally characterized using spectroscopic data and electronic circular dichroism analyses. All isolates were evaluated for their inhibitory effects on the 3-phosphoglycerate dehydrogenase (PHGDH) enzyme, which catalyzes the first committed step for the synthesis of glucose-derived serine and is associated with many kinds of cancers. Among these compounds, methyl caffeate (3) exhibited effective inhibition against PHGDH and was directly bound to PHGDH based on the microscale thermophoresis method and the cellular thermal shift assay. Further biochemical assays revealed that 3 was a noncompetitive inhibitor with respect to the substrate of 3-phosphoglycerate and exhibited a concentration-dependent inhibition. Molecular docking demonstrated that 3 coordinated in an allosteric site of PHGDH with low binding energy. Meanwhile, 3 was selectively toxic to high PHGDH-expressing cancer cell lines and could cause apoptosis of cervical cancer cells in micromolar concentrations and could obviously inhibit tumor growth in the HeLa xenograft mouse model with low toxicities. Therefore, 3 could be developed as a potential inhibitor of PHGDH for the treatment of cancers. Our present study provides information about M. nigra as a functional food or pharmaceutical supplement in the application of cancer prevention and treatment.

Expression of Glucose Metabolism-Related Proteins in Adrenal Neoplasms

PURPOSE

The aim of this study was to investigate the expression patterns of glucose metabolism-related proteins and their clinicopathologic implications in adrenal cortical neoplasms (ACN) and pheochromocytoma (PCC).

METHODS

Immunohistochemical staining was performed to evaluate glucose metabolism-related proteins (GLUT1, CAIX, hexokinase II, G6PDH, PHGDH, and SHMT1) in 132 ACN cases (115 adrenal cortical adenoma [ACA] and 17 adrenal cortical carcinoma [ACC]) and 189 PCC cases.

RESULTS

Expression levels of GLUT1 in tumor cells ([T]; p < 0.001), GLUT1 in stromal cells ([S]; p < 0.001), G6PDH (p < 0.001), and SHMT1 (p = 0.002) were higher in ACN than in PCC. GLUT1 (T; p = 0.045) and PHGDH (p = 0.043) levels were higher in ACC than in ACA. In a univariate analysis of ACN, GLUT1 (T; p = 0.017), CAIX (S; p = 0.003), and PHGDH (p = 0.009) levels were correlated with a shorter overall survival (OS). GLUT1 (T; p = 0.001) and PHGDH (p < 0.001) were related to a shorter OS in PCC. GLUT1 (T) positivity (p = 0.043) in ACN predicted a poor OS in a multivariate Cox analysis. In PCC, high GAPP score (p = 0.026), GLUT1 (T; p = 0.002), and PHGDH (p < 0.001) were independent prognostic factors for poor OS.

CONCLUSIONS

The adrenal gland tumors ACN and PCC had different expression patterns of glucose metabolism-related proteins (GLUT1, G6PDH, and SHMT1), with higher expression levels in ACN than in PCC. GLUT1 and PHGDH were significant prognostic factors in these adrenal neoplasms.

Proteomic Profiling of BRAFV600E Mutant Colon Cancer Cells Reveals the Involvement of Nucleophosmin/c-Myc Axis in Modulating the Response and Resistance to BRAF Inhibition by Vemurafenib

BRAFV600E mutations are found in approximately 10% of colorectal cancer patients and are associated with worse prognosis and poor outcomes with systemic therapies. The aim of this study was to identify novel druggable features of BRAFV600E-mutated colon cancer (CC) cells associated with the response and resistance to BRAFV600E inhibitor vemurafenib. Towards this aim, we carried out global proteomic profiling of BRAFV600E mutant vs. KRAS mutant/BRAF wild-type and double wild-type KRAS/BRAF CC cells followed by bioinformatics analyses. Validation of selected proteomic features was performed by immunohistochemistry and in silico using the TCGA database. We reveal an increased abundance and activity of nucleophosmin (NPM1) in BRAFV600E-mutated CC in vitro, in silico and in tumor tissues from colon adenocarcinoma patients and demonstrate the roles of NPM1 and its interaction partner c-Myc in conveying the resistance to vemurafenib. Pharmacological inhibition of NPM1 effectively restored the sensitivity of vemurafenib-resistant BRAF-mutated CC cells by down-regulating c-Myc expression and activity and consequently suppressing its transcriptional targets RanBP1 and phosphoserine phosphatase that regulate centrosome duplication and serine biosynthesis, respectively. Altogether, findings from this study suggest that the NPM1/c-Myc axis could represent a promising therapeutic target to thwart resistance to vemurafenib in BRAF-mutated CC.

Phosphoglycerate dehydrogenase (PHGDH) inhibitors: a comprehensive review 2015-2020

Introduction:The phosphoglycerate dehydrogenase (PHGDH), a metabolic enzyme involved in the serine synthetic pathway (SSP), appears to play a central role in supporting cancer growth and proliferation. PHGDH is a dehydrogenase whose expression in cancers was first demonstrated in 2010. Because its silencing allows a significant reduction in tumor proliferation, it appears to be a promising target in the development of new anti-cancer agents.Areas covered: In this review, we will detail PHGDH inhibitors that were reported since 2015. These compounds will be ranked according to their chemical class and their site of action. Representative examples of each series will be presented as well as their inhibitory potency in vitro and/or in vivo. Finally, their most significant biological effects will be detailed.Expert opinion: Currently, and despite significant efforts, the search for PHGDH inhibitors has not yet led to the development of compounds that can be used therapeutically. The available inhibitors have either too weak inhibitory potency or limited selectivity. Therefore, it seems crucial, given the importance of this enzyme in the progression of cancer but also in other pathologies, to pursue the development of new chemical series.

3-Phosphoglycerate dehydrogenase: a potential target for cancer treatment

BACKGROUND

Metabolic changes have been recognized as an important hallmark of cancer cells. Cancer cells can promote their own growth and proliferation through metabolic reprogramming. Particularly, serine metabolism has frequently been reported to be dysregulated in tumor cells. 3-Phosphoglycerate dehydrogenase (PHGDH) catalyzes the first step in the serine biosynthesis pathway and acts as a rate-limiting enzyme involved in metabolic reprogramming. PHGDH upregulation has been observed in many tumor types, and inhibition of PHGDH expression has been reported to inhibit the proliferation of PHGDH-overexpressing tumor cells, indicating that it may be utilized as a target for cancer treatment. Recently identified inhibitors targeting PHGDH have already shown effectiveness. A further in-depth analysis and concomitant development of PHGDH inhibitors will be of great value for the treatment of cancer.

CONCLUSIONS

In this review we describe in detail the role of PHGDH in various cancers and inhibitors that have recently been identified to highlight progression in cancer treatment. We also discuss the development of new drugs and treatment modalities based on PHGDH targets. Overexpression of PHGDH has been observed in melanoma, breast cancer, nasopharyngeal carcinoma, parathyroid adenoma, glioma, cervical cancer and others. PHGDH may serve as a molecular biomarker for the diagnosis, prognosis and treatment of these cancers. The design and development of novel PHGDH inhibitors may have broad implications for cancer treatment. Therapeutic strategies of PHGDH inhibitors in combination with traditional chemotherapeutic drugs may provide new perspectives for precision medicine and effective personalized treatment for cancer patients.

A retrospective overview of PHGDH and its inhibitors for regulating cancer metabolism

Emerging evidence suggests that cancer metabolism is closely associated to the serine biosynthesis pathway (SSP), in which glycolytic intermediate 3-phosphoglycerate is converted to serine through a three-step enzymatic transformation. As the rate-limiting enzyme in the first step of SSP, phosphoglycerate dehydrogenase (PHGDH) is overexpressed in various diseases, especially in cancer. Genetic knockdown or silencing of PHGDH exhibits obvious anti-tumor response both in vitro and in vivo, demonstrating that PHGDH is a promising drug target for cancer therapy. So far, several types of PHGDH inhibitors have been identified as a significant and newly emerging option for anticancer treatment. Herein, this comprehensive review summarizes the recent achievements of PHGDH, especially its critical role in cancer and the development of PHGDH inhibitors in drug discovery.

The ins and outs of serine and glycine metabolism in cancer

Cancer cells reprogramme their metabolism to support unrestrained proliferation and survival in nutrient-poor conditions. Whereas non-transformed cells often have lower demands for serine and glycine, several cancer subtypes hyperactivate intracellular serine and glycine synthesis and become addicted to de novo production. Copy-number amplifications of serine- and glycine-synthesis genes and genetic alterations in common oncogenes and tumour-suppressor genes enhance serine and glycine synthesis, resulting in high production and secretion of these oncogenesis-supportive metabolites. In this Review, we discuss the contribution of serine and glycine synthesis to cancer progression. By relying on de novo synthesis pathways, cancer cells are able to enhance macromolecule synthesis, neutralize high levels of oxidative stress and regulate methylation and tRNA formylation. Furthermore, we discuss the immunosuppressive potential of serine and glycine, and the essentiality of both amino acids to promoting survival of non-transformed neighbouring cells. Finally, we point to the emerging data proposing moonlighting functions of serine- and glycine-synthesis enzymes and examine promising small molecules targeting serine and glycine synthesis.

Shared and unique metabolic features of the malignant and benign thyroid lesions determined with use of 1H HR MAS NMR spectroscopy

The purpose of this work was to investigate the distinct and common metabolic features of the malignant and benign thyroid lesions in reference to the non-transformed tissue from the contralateral gland (chronic thyroiditis and colloid goiter). 1H HR MAS NMR spectra of 38 malignant lesions, 32 benign lesions and 112 samples from the non-tumoral tissue (32 from chronic thyroiditis and 80 samples from colloid goiter) were subjected both to multivariate and univariate analysis. The increased succinate, glutamine, glutathione, serine/cysteine, ascorbate, lactate, taurine, threonine, glycine, phosphocholine/glycerophosphocholine and decreased lipids were found in both lesion types in comparison to either colloid goiter or chronic thyroiditis. The elevated glutamate and choline, and reduced citrate and glucose were additionally evident in these lesions in reference to goiter, while the increased myo-inositol-in comparison to thyroiditis. The malignant lesions were characterized by the higher alanine and lysine levels than colloid goiter and thyroiditis, while scyllo-inositol was uniquely increased in the benign lesions (not in cancer) in comparison to both non-tumoral tissue types. Moreover, the benign lesions presented with the unique increase of choline in reference to thyroiditis (not observed in the cancerous tissue). The metabolic heterogeneity of the non-tumoral tissue should be considered in the analysis of metabolic reprogramming in the thyroid lesions.

High Phosphoglycerate Dehydrogenase Expression Induces Stemness and Aggressiveness in Thyroid Cancer

Background: We examined the changes in glucose metabolites of papillary thyroid cancer (PTC) and identified phosphoglycerate dehydrogenase (PHGDH) as a potential target. The role of PHGDH in the proliferation and tumorigenesis of thyroid cancer cells and its clinical significance were analyzed. Methods: Glucose metabolites of various thyroid tissues were analyzed via targeted metabolomics analysis. In vitro experiments using shPHGDHs, inhibitor (NCT503), or PHGDH overexpression in thyroid cell lines (BCPAP, 8505C, and Nthy-Ori) were performed. In vivo experiments were performed by using shPHGDH. Human tissue samples and The Cancer Genome Atlas (TCGA) data were used to validate the experimental findings. Results:PHGDH knockdown in BCPAP and 8505c cell lines significantly inhibited cell viability, colony formation, and tumor spheroid formation compared with the control. In addition, treatment with NCT503 showed similar results. PHGDH inhibition by both knockdown and treatment with NCT503 significantly inhibited the expression of embryonic cancer stemness markers (Oct4, Sox2, KLF4, and Nanog). PHGDH overexpression in Nthy-Ori cells significantly increased cell viability and colony formation. The stemness markers were significantly increased after PHGDH overexpression. PHGDH knockdown significantly inhibited tumor growth in an in vivo mouse xenograft study using 8505c cells. The protein expression of Oct4 in tumors was significantly reduced after PHGDH knockdown. The associations between PHGDH expression and stemness markers were confirmed in the TCGA data and human thyroid tissue samples. Positive PHGDH protein expression was associated with metastases of PTC. Conclusions:PHGDH expression is induced in thyroid cancer and is associated with stemness and aggressiveness of PTC.

PHGDH as a mechanism for resistance in metabolically-driven cancers

At the forefront of cancer research is the rapidly evolving understanding of metabolic reprogramming within cancer cells. The expeditious adaptation to metabolic inhibition allows cells to evolve and acquire resistance to targeted treatments, which makes therapeutic exploitation complex but achievable. 3-phosphoglycerate dehydrogenase (PHGDH) is the rate-limiting enzyme of de novo serine biosynthesis and is highly expressed in a variety of cancers, including breast cancer, melanoma, and Ewing’s sarcoma. This review will investigate the role of PHGDH in normal biological processes, leading to the role of PHGDH in the progression of cancer. With an understanding of the molecular mechanisms by which PHGDH expression advances cancer growth, we will highlight the known mechanisms of resistance to cancer therapeutics facilitated by PHGDH biology and identify avenues for combatting PHGDH-driven resistance with inhibitors of PHGDH to allow for the development of effective metabolic therapies.

Role of global aberrant alternative splicing events in papillary thyroid cancer prognosis

BACKGROUND

Alternative splicing events have been increasingly reported for anomalous perturbations in various cancers, including papillary thyroid cancer (PTC).

METHODS

Integration analysis of RNA sequencing and clinical information were utilized to identify survival associated splicing events in PTC. Then, several prognosis-related splicing events were submitted to develop moderate predictors for survival monitoring by using least absolute shrinkage and selection operator model. In addition, several biomedical computational algorithms were conducted to identify pathways enriched by genes with prognostic splicing events and construct regulatory network dominated by splicing factors.

RESULTS

Survival analysis in 496 PTC patients indicated that TNM stage, tumor stage, distant metastasis and tumor status were significantly correlated with PTC patients' progression-free interval. 2799 splicing events were identified as prognostic molecular events. Functional enrichment analysis suggested that prognostic splicing events are associated with several energy metabolism-related processes. Based on these prognostic events, several prognostic signatures were developed. The final prognostic signature acted as an independent prognostic factor after adjusting for several clinical parameters. Interestingly, splicing regulatory network was constructed to display potential regulatory mechanisms of splicing events in PTC.

CONCLUSIONS

Our analysis provides the status of splicing events involved in the progression and may represent an underappreciated hallmark of PTC.

Metabolic reprogramming and its clinical application in thyroid cancer

Warburg found that tumor cells exhibit high-level glycolysis, even under aerobic condition, which is known as the ‘Warburg effect’. As systemic changes in the entire metabolic network are gradually revealed, it is recognized that metabolic reprogramming has gone far beyond the imagination of Warburg. Metabolic reprogramming involves an active change in cancer cells to adapt to their biological characteristics. Thyroid cancer is a common endocrine malignant tumor whose metabolic characteristics have been studied in recent years. Some drugs targeting tumor metabolism are under clinical trial. This article reviews the metabolic changes and mechanisms in thyroid cancer, aiming to find metabolic-related molecules that could be potential markers to predict prognosis and metabolic pathways, or could serve as therapeutic targets. Our review indicates that knowledge in metabolic alteration has potential contributions in the diagnosis, treatment and prognostic evaluation of thyroid cancer, but further studies are needed for verification as well.

SHMT1 inhibits the metastasis of HCC by repressing NOX1-mediated ROS production

Background

Hepatocellular carcinoma (HCC) is the most major type of primary hepatic cancer. Serine hydroxymethyltransferase 1 (SHMT1) is recently found to play critical roles in human cancers including lung cancer, ovarian cancer and intestinal cancer. However, the expression, function and the underlying mechanisms of SHMT1 in HCC remain uncovered.

Methods

qRT-PCR, immunohistochemistry and immunoblotting were performed to detect the expression of SHMT1 in HCC tissues and cell lines. HCC cell migration and invasion were determined by Boyden chamber and Transwell assay in vitro, and tumor metastasis was assessed via lung metastasis model in mice. The expression of key factors involved in epithelial-to-mesenchymal transition (EMT) process was evaluated by western blotting.

Results

In this study, data mining of public databases and analysis of clinical specimens demonstrated that SHMT1 expression was decreased in HCC. Reduced SHMT1 level was correlated with unfavorable clinicopathological features and poor prognosis of HCC patients. Gain- and loss-of-function experiments showed that SHMT1 overexpression inhibited the migration and invasion of HCCLM3 cells while SHMT1 knockdown enhanced the metastatic ability of Hep3B cells. Furthermore, qRT-PCR and western blotting showed that SHMT1 inhibited EMT and matrix metallopeptidase 2 (MMP2) expression. In vivo experiments showed that SHMT1 suppressed the lung metastasis of HCC cells in mice. Mechanistically, SHMT1 knockdown enhanced reactive oxygen species (ROS) production, and thus promoted the motility, EMT and MMP2 expression in Hep3B cells. Furthermore, NADPH oxidase 1 (NOX1) was identified to be the downstream target of SHMT1 in HCC. NOX1 expression was negatively correlated with SHMT1 expression in HCC. Rescue experiments revealed that NOX1 mediated the functional influence of SHMT1 on HCC cells.

Conclusions

These data indicate that SHMT1 inhibits the metastasis of HCC by repressing NOX1 mediated ROS production.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1067-5) contains supplementary material, which is available to authorized users.

PSPH Mediates the Metastasis and Proliferation of Non-small Cell Lung Cancer through MAPK Signaling Pathways

Growing evidence indicates that phosphoserine phosphatase (PSPH) is up-regulated and correlates with prognosis in multiple types of cancer. However, little is known about the roles of PSPH in NSCLC. Thus, the aim of the present study was to demonstrate the expression of PSPH in human NSCLC and reveal its biological functions and the underlying mechanisms. qRT-PCR, western blot and immunohistochemistry were used to assess the expression of NSCLC patient specimens and NSCLC cell lines. The functions of PSPH in migration and invasion were determined using trans-well and wound-healing assays. Cell proliferation capacity was performed by cell counting kit-8 (CCK-8), colony formation assays and cell cycle analysis. We demonstrated that PSPH was overexpressed in NSCLC specimens compared with the adjacent non-tumorous specimens, and high expression of PSPH was associated with clinical stage, metastasis and gender in NSCLC. Decreased expression of PSPH inhibited NSCLC cells migration, invasion and proliferation. Most importantly, further experiments demonstrated that PSPH might regulate NSCLC progress through MAPK signaling pathways. Lastly, immunohistochemistry (IHC) revealed that the PSPH expression level was positively correlated with the clinical stage in NSCLC patients. These results suggest that PSPH may act as a putative oncogene and a potential therapeutic target in NSCLC.

GCSH antisense regulation determines breast cancer cells' viability

Since it is known that cancer cells exhibit a preference for increased glycine consumption, the respective glycine metabolizing enzymes are in focus of many research projects. However, no cancer associated studies are available for the Glycine Cleavage System Protein H (GCSH) to date. Our initial analysis revealed a GCSH-overexpression of the protein-coding transcript variant 1 (Tv1) in breast cancer cells and tissue. Furthermore, a shorter (391 bp) transcript variant (Tv*) was amplified with an increased expression in healthy breast cells and a decreased expression in breast cancer samples. The Tv1/Tv* transcript ratio is 1.0 in healthy cells on average, and between 5–10 in breast cancer cells. Thus, a GCSH-equilibrium at the transcript level is likely conceivable for optimal glycine degradation. A possible regulative role of Tv* was proven by Tv1-Tv*-RNA-binding and overexpression studies which consequently led to serious physiological alterations: decreased metabolic activity, release of the lactate dehydrogenase, increased extracellular acidification, and finally necrosis as a result of impaired plasma membranes. In contrast, Tv1-overexpression led to an additional increase in cellular vitality of the tumor cells, primarily due to the acceleration of the mitochondrial glycine decarboxylation activity. Ultimately, we provide the first evidence of a sensitive GCSH-antisense regulation which determines cancerous cell viability.

Enhanced phosphocholine metabolism is essential for terminal erythropoiesis

Red cells contain a unique constellation of membrane lipids. Although much is known about regulated protein expression, the regulation of lipid metabolism during erythropoiesis is poorly studied. Here, we show that transcription of PHOSPHO1, a phosphoethanolamine and phosphocholine phosphatase that mediates the hydrolysis of phosphocholine to choline, is strongly upregulated during the terminal stages of erythropoiesis of both human and mouse erythropoiesis, concomitant with increased catabolism of phosphatidylcholine (PC) and phosphocholine as shown by global lipidomic analyses of mouse and human terminal erythropoiesis. Depletion of PHOSPHO1 impaired differentiation of fetal mouse and human erythroblasts, and, in adult mice, depletion impaired phenylhydrazine-induced stress erythropoiesis. Loss of PHOSPHO1 also impaired phosphocholine catabolism in mouse fetal liver progenitors and resulted in accumulation of several lipids; adenosine triphosphate (ATP) production was reduced as a result of decreased oxidative phosphorylation. Glycolysis replaced oxidative phosphorylation in PHOSPHO1-knockout erythroblasts and the increased glycolysis was used for the production of serine or glycine. Our study elucidates the dynamic changes in lipid metabolism during terminal erythropoiesis and reveals the key roles of PC and phosphocholine metabolism in energy balance and amino acid supply.

The Nutrient-Sensing Hexosamine Biosynthetic Pathway as the Hub of Cancer Metabolic Rewiring

Alterations in glucose and glutamine utilizing pathways and in fatty acid metabolism are currently considered the most significant and prevalent metabolic changes observed in almost all types of tumors. Glucose, glutamine and fatty acids are the substrates for the hexosamine biosynthetic pathway (HBP). This metabolic pathway generates the “sensing molecule” UDP-N-Acetylglucosamine (UDP-GlcNAc). UDP-GlcNAc is the substrate for the enzymes involved in protein N- and O-glycosylation, two important post-translational modifications (PTMs) identified in several proteins localized in the extracellular space, on the cell membrane and in the cytoplasm, nucleus and mitochondria. Since protein glycosylation controls several key aspects of cell physiology, aberrant protein glycosylation has been associated with different human diseases, including cancer. Here we review recent evidence indicating the tight association between the HBP flux and cell metabolism, with particular emphasis on the post-transcriptional and transcriptional mechanisms regulated by the HBP that may cause the metabolic rewiring observed in cancer. We describe the implications of both protein O- and N-glycosylation in cancer cell metabolism and bioenergetics; focusing our attention on the effect of these PTMs on nutrient transport and on the transcriptional regulation and function of cancer-specific metabolic pathways.

Downregulation of glycine decarboxylase enhanced cofilin-mediated migration in hepatocellular carcinoma cells

Metabolic reprogramming is a hallmark of cancer. Glycine decarboxylase (GLDC), an oxidoreductase, plays an important role in amino acid metabolism. While GLDC promotes tumor initiation and proliferation in non-small cell lung cancer and glioma and it was reported as a putative tumor suppressor gene in gastric cancer, the role of GLDC in hepatocellular carcinoma (HCC) is unknown. In the current study, microarray-based analysis suggested that GLDC expression was low in highly malignant HCC cell lines, and clinicopathological analysis revealed a decrease in GLDC in HCC tumor samples. While the knockdown of GLDC enhanced cancer cell migration and invasion, GLDC overexpression inhibited them. Mechanistic studies revealed that GLDC knockdown increased the levels of reactive oxygen species (ROS) and decreased the ratio of glutathione/oxidized glutathione (GSH/GSSG), which in turn dampened the ubiquitination of cofilin, a key regulator of actin polymerization. Consequently, the protein level of cofilin was elevated, which accounted for the increase in cell migration. The overexpression of GLDC reversed the phenotype. Treatment with N-acetyl-L-cysteine decreased the protein level of cofilin while treatment with H₂O₂ increased it, further confirming the role of ROS in regulating cofilin degradation. In a tumor xenographic transplant nude mouse model, the knockdown of GLDC promoted intrahepatic metastasis of HCC while GLDC overexpression inhibited it. Our data indicate that GLDC downregulation decreases ROS-mediated ubiquitination of cofilin to enhance HCC progression and intrahepatic metastasis.

Glycine: a non-invasive imaging biomarker to aid magnetic resonance spectroscopy in the prediction of survival in paediatric brain tumours

Paediatric brain tumours have a high mortality rate and are the most common solid tumour of childhood. Identification of high risk patients may allow for better treatment stratification. Magnetic Resonance Spectroscopy (MRS) provides a non-invasive measure of brain tumour metabolism and quantifies metabolite survival markers to aid in the clinical management of patients. Glycine can be identified using MRS and has been recently found to be important for cancer cell proliferation in tumours making it a valuable prognostic marker. The aims of this study were to investigate glycine and its added value to MRS as a prognostic marker for paediatric brain tumours in a clinical setting.

116 children with newly diagnosed brain tumours were examined with short echo-time MRS at the Birmingham Children’s Hospital and followed up for five years. Survival analysis was performed using Cox regression on the entire metabolite basis set with focus on glycine and three other established survival markers for comparison: n-acetylaspartate, scyllo-inositol and lipids at 1.3 ppm. Multivariate Cox regression was used in conjunction with risk values to establish if glycine added prognostic power when combined to the established survival markers.

Glycine was found to be a marker of poor prognosis in the cohort (p < 0.05) and correlated with tumour grade (p < 0.01). The addition of glycine improved the prognostic power of MRS compared to using the combination of established survival markers alone.

Tumour glycine was found to improve the MRS prediction of reduced survival in paediatric brain tumours aiding the non-invasive assessment of these children.

Differential expression of serine and glycine metabolism-related proteins between follicular neoplasm and Hürthle cell neoplasm

The aim of the study was to investigate the expression of serine/glycine-related proteins in Hürthle cell neoplasm (HCN) and follicular neoplasm (FN) and to explore its associated implications. Tissue microarrays were constructed with 265 cases of FN (follicular carcinoma [FC]: 112 and follicular adenoma [FA]: 153) and 107 cases of HCN (Hürthle cell carcinoma [HCC]: 27 and Hürthle cell adenoma [HCA]: 80). The serine/glycine-related proteins PHGDH, PSAT1, SHMT1, and GLDC were evaluated using immunohistochemical staining. The expression of SHMT1 and PHGDH was higher in HCN compared to FN (P<0.001 and P=0.048). SHMT1 expression was highest in HCC, followed by HCA, FA, and FC (P<0.001), and PHGDH expression was highest in HCA, followed by HCC, FC, and FA (P=0.041). In FC, SHMT1 negativity was associated with extrathyroidal extension (P=0.019). In univariate analysis, PSAT1 negativity was associated with shorter overall survival (P<0.001). The expression of serine/glycine-related proteins differed between FN and HCN. The expression of both SHMT1 and PHGDH was higher in HCN compared to FN. The clinical implications of this study are that the serine/glycine metabolism pathway could be a possible therapeutic target in HCC.

Metabolic Alterations of Thyroid Cancer as Potential Therapeutic Targets

Thyroid cancer (TC) is the most frequent endocrine tumor with a growing incidence worldwide. Besides the improvement of diagnosis, TC increasing incidence is probably due to environmental factors and lifestyle modifications. The actual diagnostic criteria for TC classification are based on fine needle biopsy (FNAB) and histological examination following thyroidectomy. Since in some cases it is not possible to make a proper diagnosis, classical approach needs to be supported by additional biomarkers. Recently, new emphasis has been given to the altered cellular metabolism of proliferating cancer cells which require high amount of glucose for energy production and macromolecules biosynthesis. Also TC displays alteration of energy metabolism orchestrated by oncogenes activation and tumor suppressors inactivation leading to abnormal proliferation. Furthermore, TC shows significant metabolic heterogeneity within the tumor microenvironment and metabolic coupling between cancer and stromal cells. In this review we focus on the current knowledge of metabolic alterations of TC and speculate that targeting TC metabolism may improve current therapeutic protocols for poorly differentiated TC. Future studies will further deepen the actual understandings of the metabolic phenotype of TC cells and will give the chance to provide novel prognostic biomarkers and therapeutic targets in tumors with a more aggressive behavior.

Induced-Decay of Glycine Decarboxylase Transcripts as an Anticancer Therapeutic Strategy for Non-Small-Cell Lung Carcinoma

Self-renewing tumor-initiating cells (TICs) are thought to be responsible for tumor recurrence and chemo-resistance. Glycine decarboxylase, encoded by the GLDC gene, is reported to be overexpressed in TIC-enriched primary non-small-cell lung carcinoma (NSCLC). GLDC is a component of the mitochondrial glycine cleavage system, and its high expression is required for growth and tumorigenic capacity. Currently, there are no therapeutic agents against GLDC. As a therapeutic strategy, we have designed and tested splicing-modulating steric hindrance antisense oligonucleotides (shAONs) that efficiently induce exon skipping (half maximal inhibitory concentration [IC₅₀] at 3.5–7 nM), disrupt the open reading frame (ORF) of GLDC transcript (predisposing it for nonsense-mediated decay), halt cell proliferation, and prevent colony formation in both A549 cells and TIC-enriched NSCLC tumor sphere cells (TS32). One candidate shAON causes 60% inhibition of tumor growth in mice transplanted with TS32. Thus, our shAONs candidates can effectively inhibit the expression of NSCLC-associated metabolic enzyme GLDC and may have promising therapeutic implications.